Priority is claimed with respect to European application No. 99810065.5-1256 filed Jan. 26, 1999, the disclosure of which is incorporated herein by reference.
The invention relates to a device for opening and depositing a folded signature onto a moving conveyor, particularly a collecting chain, which device comprises two opening rollers with axes that extend essentially parallel to the conveying direction of the conveyor and respectively open one signature and deposit it with the opened side first in a downwardly direction onto the conveyor, wherein the signatures are pre-accelerated in the conveying direction of the conveyor.
Swiss Patent CH-A-617 905 discloses a device that allows paper signatures with off-center folds to be opened and deposited on a collecting chain. Such device comprises a continuously rotating take-up roller, as well as two opening rollers, arranged below it, which open the signatures and drop them onto the conveyor chain. In this case, the first opening roller seizes an overlay fold of the signature and the second opening roller subsequently seizes the other, shorter leg of the signature. Following the opening, the signatures are dropped directly downward, onto the moving conveyor chain. Carriers on the conveyor chain will move the signatures along. In the process, the signatures are pre-accelerated somewhat by the moving chain.
Past experience has shown that thin, four-page signatures can be dropped vertically and without pre-acceleration onto a collecting chain. However, at speeds higher than approximately 16,000 copies per hour, the signatures are compressed during the acceleration by the carriers to such a degree that they can no longer be accelerated reliably. Thus, it is the goal for high-production machines to have the smallest chain pitch, meaning the distance between two successive carriers and the back length of the format to be processed. Essentially, no time is available for accelerating the signatures with the aid of friction on the moving collecting chain. Thus, a further increase in output is not possible with this device, especially for thin signatures.
A similar device of the generic type is known from Swiss Patent CH-A-493 337. With this device, the opened signatures are deposited on a knife folder and are pre-accelerated through a movement of this knife folder. However, the acceleration with such a knife folder has not proven successful in practical operations. In addition, the vertically downward pointing speed component for statically charged signatures is missing here, which component is required for such signatures.
It is an object of the invention to create a device of the aforementioned type, which can still be produced cheaply and allows for a further increase in output.
The above and other objects are achieved in accordance with the invention by the provision of a device for opening and depositing folded signatures onto a moving conveyor for conveying the folded signatures in a conveying direction, comprising: two opening rollers each having a rotational axis that extends essentially parallel to the conveying direction of the conveyor and having means for opening the respective signatures and depositing the signatures with an opened side first in a downward direction onto the conveyor, wherein the opening rollers further include pre-accelerating means for pre-accelerating the respective signatures in the conveying direction.
With the device according to the invention, the signatures are respectively pre-accelerated in the horizontal direction by the opening rollers and prior to being dropped. Thus, the signatures are not dropped first and then accelerated, as is the case in the prior art, but are accelerated horizontally on the opening rollers before being dropped. Thus, they are provided with a horizontal as well as a vertical speed component. The acceleration operation follows immediately after the opening operation and on the opening rollers. The essential feature is that the signatures can be carried along without interruption until they leave the opening rollers. The acceleration operation consequently occurs downstream, immediately after the opening operation.
The opening rollers preferably accelerate the signatures in the horizontal direction when the lower, opened side of the signatures already overlaps the conveyor chain. After the signatures are dropped, they are immediately taken over by the conveyor chain and are transported along by this chain. Experiments have shown that even very thin signatures can be safely processed with a higher output than has been possible so far.
The fact that the vertical drop component is retained is seen as another essential advantage of the device according to the invention. As a result, it is also possible to process signatures with electrostatic charge, which must be dropped with a predetermined minimum vertical speed onto the conveyor chain or the collecting chain. This is hardly possible with a pre-acceleration by means of the so-called knife folder.
According to one embodiment of the invention, a particularly cost-effective and operationally secure implementation of the invention is ensured if accelerating rollers are provided which are respectively arranged at an angle on the shafts for the two opening rollers. With the aid of these accelerating rollers, the signatures are seized on the outside immediately following the opening by the opening disks and are accelerated in the conveying direction of the conveyor. It is preferable if these accelerating rollers are designed as profile rollers. In that case, signatures having a varied thickness can be processed without requiring a device change-over, provided at least one of the angled accelerating rollers has an elastic support, as detailed for one modification of the invention.
According to another embodiment of the invention, at least two driven cylinders are provided, which are respectively arranged on the opening disks of one opening roller and which operate jointly to seize and accelerate respectively one signature. With this modification, the means for accelerating the signatures are thus arranged directly on the opening disks. One essential advantage of this modification is that even very small formats can be processed. If these rollers have a design similar to that of a beehive, then the signatures are accelerated with a continuous increase when seized with these rollers. Thus, the horizontal speed is low at the start and at a maximum at the end.
Additional advantageous features follow from, the following detailed description, considered in conjunction with the accompanying drawings.